Abstract: Objective · To study the effect of sumoylation on the structure, stability and activity of human thymine DNA glycosylase (TDG).
Methods · Expression and purification systems were established for obtaining SUMO-1-TDG protein with high purity which can be used for crystal
screening and activity detection. Structure of SUMO-1-TDG was solved after crystal screening, diffraction data collection and structure analysis. The
change of TDG stability led by sumoylation was detected through a protein thermal shift assay. In addition, an activity assay was applied to investigate the
effect of sumoylation on the activity of TDG. Results · A high-resolution structure of SUMO-1-TDG which could clearly describe the interaction between
TDG and SUMO-1 was solved. The melting temperature (Tm) value of SUMO-1-TDG increased by about 16 ℃ and the catalytic activity increased by 9.70%,
comparing with TDG protein. Conclusion · SUMO-1 binds to TDG to modify the intermolecular interaction of amino acids near the binding site, and
further participates in the regulation of the stability and catalytic activity of TDG protein.

Key words: thymine DNA glycosylase, sumoylation, crystal structure, thermal shift assay, activity assay